A big problem in the implementation of robots and the like in manufacturing and particularly assembly has been their lack of precision in dimensional placement. Such lack of precision in their arm locations is not surprising considering that they must have multiple flexured joints each one of which has to move in precise manner and often with coordinate calculations corrected by computer in order to put the end of the arm at a given point in space. Such precisions have led to high prices for certain types of accurately positionable robots (still short of the mark in many cases), or conversely an inability to perform certain desired applications.
The problem is otherwise defined as the stack up of dimensional uncertainties due to encoder error and mechanical sag or deflection anywhere in the system. While such deflections can be statically compensated, the problem becomes enormous when varient parts of different weights are lifted and rapidly accelerated and de-accelerated.
All of these problems are obviated in large measure by the invention here disclosed.
The goal of the disclosed invention is increased accuracy of positioning as in assembly or parts transfer at decreased cost of the manipulator. Also universality to many different part groupings or manipulators is also attained since one optical guidance system can function on many different types of automation systems.
Disclosed herein are methods and apparatus to provide an accurate external reference coordinate system for the robot (or other machine) which the robot system can utilize rather than relying on mechanical axes. This then essentially allows mechanically bad robots to become accurately positionable. In the grid reference case, for example, it also projects onto the part a certain reference system on which a sensor on the robot can interact with as well. This then can be used to link up the relationships of the two to each other, namely the robot and the part.
Another goal of the invention is to provide means for correcting droop and deflection in robot or co-ordinate measuring machine axes to improve their accuracy at a given cost.
The disclosed invention basically concerns the projection of specialized grid networks, directed laser beams or other light beams in space to provide a co-ordinate network or homing type function for the robot arm.